Preparation of a solid diphenylamine antioxidant



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United States Patent BREBARA'IION OF A SOLID DIBHENYLAMINE ANTIQXIDANT lie e Falls, Ohio, assigno'r's to e F Goodrich gdlrlip tiliy; 'Nw York, "TN." Y.,' a "corporat on of New 9 D aw n Ali lica i h ch 3 .8 4, -sgfiamqpfls;

This invention relates to a method for producing a solid, dry antioxidant useful as an 'age -resistor 'in rub bery compositions and other organic materials subject to oxidation. In particular, the present invention relates to a method for producing a solid, frangible, dry composition comprising a dialkylated diarylamine, such as dioctyl diphenylamine, which can readily be dry mixed with rubber and other compounding ingredients on a roll mill or in a Banbury mixer and the like.

when compounding rubber with other ingredients on the mill, it generally is preferred to use solids since they 93 112 1: e fi lyhandled. Many Of the best antioxidants such as amines, however, are obtained as reaction mix- I tures in liquid form which are difiicult to solidify. Es-

pecially is this of the diallgylated diarylamines such as p,p-dioctyl 'diphenylamine which is shown or suggested in U. S. Le t ters Patent to Craig 2,009,480 and Ha li 2 3- 6 hs whi h se e to i h$hat th reassessed l s ltl h lh hiheh assemb y prepares hr rs- $99 5? .1 a e i a l ah a Q s ish h y ehe 9? ha hu ah ti diPhWfiiWW hfthe Pa .h e of F a-Ca e ca a s a elev e t ths w th he 0h l l r' e r At hl said 19 'n a awas a phenylanirne in addition to the desired pro ct, the ,-,R li sh /ls iih T h eheh hsh s s hshh yhh h h h e se lr hr s stillation. Depending onthe method of introducing the reactants, the mol ratios, and the like, more or less hf the above products will be obtained, but, even with the oif ther u e hs i e a h aa h 1 e hih it th hi a laqa Mer r h t f hdh t te tihh ta awa th I s a h a th hh h h y ihh hhhhh i raw Qi n Y hhhhs hh cti h exposed at os- I ny unreactddiph 'a h fi -e h h I Wha .5 h h e h te shth h 0 errocls of timeQth'at is, fors months.

g of thefliqui d'will not produce afs ol id jinn I :eks'. Moreoyer, subsequ nt'rernoval of a 'a1 an; unt ,of the riftono o lylkl lplleliyl m ne will at e e u r at sp e ai ehah ef. M .7 He s eh hhc raaahss e hlprast h I V the reaction mixture can be crys- "th lh hhh h h th ha ih a i... hht

s'olid' containing'from 80 to 100% dihahhe hai s he ,hthhees y A LJi NlIIlIK diphenylamine, and having a set point of from 73 to 100 CYl Io'wever, from 30 to 49% or more of the dioctyl diphenylarnine compound remains in the methaiiol ordiisobi tylene. Extensive apparatus is required for'the recovery of the solvent so that the process is impracticaleven ignoring the initial cos-t of solvent. Moreover, after recovery of the solvent, the residual liquid cannot be solidified even thoughit contains an appreciable an onnt of dioctyl diphenylamine. Furthermore, these em a h s hhl hh' iype'pmceshe's and do s nd thei YQS IQ s'hdilY tohigh production requirements.

Ac rd ingly, it is a primary object of the present inyentiontoproyide a method for readilypbtaining' a solid antioxidant compris'ing' a diallcylated' diphen'ylar'nine. I s" ano he Qhie i i his in e i n P f method for co inuou'sly treating a liquid reaction mixtu e whia hihs an w diphe' yl m n to Ob a n a soli fi h 'thl 'hhi ct i th pro de a me hod fo produ an antioxidant comprising p,p."- dioctyl"diphenylarnine in 5 6 blfldl' 91 i i Y These anfother objects and advantages of the present ri hl h W l b om ma he hreh l'slhll d iii th'e art from thefollowin'g', detailed description andexahi e It has now been discovered according to the present inventioh'that :th ediificnltieis allud d tohereinaboye can be readilyoverc'o'meby cooliii' ated "diarylaiiiie liq re p v an h h h h hh h s hhii i a l f e mah alkylated diarylarnines"l'iavel;eenremoyed,' within the 'tejfrip'e'rature range of from the initial crystallization point of the miirture to the set poi nt of'the dialliylated diarylamine toobtain 'a semisolid'and rapidly cooling said ser'fiislolid to a temperature substantially belowjthe initial c'rystalliiation paint r them; e to obtain a ug, frangible, dry product. By the method disclosed herein about 55 to of the latent heaffof crystallization of the "mixture is removed in the first stepandthe balance in the" second step. The re'sultingriiaterial can be'readily broken 'up in a gii'nding machine to the s ize desired.

It is nongreasy and can be easily handled on a rubber mill with the customary 'niater'i'alserriployd in compounding rubber.

The amines used to react with the alkenes to form the liquid reaction mixtures from which thesolid ant iorih dants are obtained are diarylamines havingthe'forinula:

R1 R2 R3 R4 where R1, R2, R3 and R4 are selected from the group consisting of halogen, hydrogen and alkyl having'from Specific examples of suitable m s e i h y ar hl 0 9 9 fi nh h hmi b- "methyl diphenylamine, o,o-dirnethy1 diphenylarnine, o,rr 1-:methyl,'propyl diphenylaniine, o,o,m,m'-tetraiiiethyl diphenylam'ine, 'o,o'-rnethyl ethyl diphenylamine, 0,0- chloroethyl diphenylamine and the' like. The 'al ken es are selected from the group of alkenes having from 6 'to 12'carbon' atoms and, preferably, are branch chained alkenes. Suitable alkenes are hexene, 3-rhethyl-1-hex- 'en'e, 'diisobutylene,' 2,5-dimethyl hexene, l-heptene, 2- ethyI-B-methyl-I-butene, 2-dimethyl-4-dimethyl 1-amylene and their isomers and so forth.

The diarylamines and alkenes are easily reacted in 11101 ratios of 1:2 and, preferably with anexCess of the alkene, in the 'presenceof a minor amount"(.Ol-0.l mol) of a FriedeLCrafts'catalyst'such as aluminum chloride or zinc chloride at temperatures of from' 15.0 to'250 C; with agitation ,under pressure, i. e., in an autoclave, and under anhydrous conditions for about an hour. Of course,

the temperatures and times can be varied somewhat depending on equipment employed, quantities of reactants and the like.

While an excess of alkene over diarylamine is desired, it is unnecessary to use a large excess such as 3 to 4 mols of alkene to 1 mol of amine nor a large excess of catalyst. Moreover, the amine should be charged to the reactor followed by the catalyst and then the alkene introduced in order to obtain the best yields. Reversing the procedure of introducing the reactants or reacting under refluxing conditions will result in unsatisfactory yields of the dialkylated diarylamine.

At the completion of the reaction the reaction mixture can be cooled slightly and the alkene flashed off. Alternatively it can be distilled and the alkene recovered. The liquid mixture is then permitted to cool below the boiling point of water, about 90 C., and washed with water and 50% caustic soda solution. The mixture is then stripped of any unreacted diarylamine and a substantial portion of the monoalkylated diarylamine. The remaining portion of the reaction mixture or residue is then ready to be solidified. Although the fractionation of the reaction mixture can be conducted until the residue is essentially dialkylated diarylamine, it is only necessary to reduce the content of the monoalkylated diarylamine to from 2 to to obtain a mixture which can be solidified and which will have the desired antioxidant properties.

After stripping, the hot liquid residue can be cooled until it reaches a temperature slightly above the set point of the pure dialkylated diarylamine and then agitated vigorously while being cooled within the temperature range of from its initial crystallization point to the set point of the pure dialkylated diarylamine. The initial crystallization point of the mixture is a few degrees below its set point. Alternatively the hot liquid can be cooled while agitated to a temperature within the above range. Within a short time the liquid will have formed into a slush or semisolid and then is further cooled substantially below its initial crystallization point to obtain a solid, frangible, dry product. The hot stripped liquid residue of the reaction mixture can be pumped continuously through a pipe or tube or other means having heat exchange elements containing a coolant and continuously agitated by means of a stirrer or other means, or through a screw type conveyor having agitating elements and heat exchanging elements, to emerge or be extruded as a semisolid onto conveying or chilling means which op crates at a much lower temperature than the agitating means to rapidly cool or chill to form a solid.

During the first cooling step the liquid mixture is agitated vigorously while it is cooled by being in heat exchange relationship with a coolant at a temperature well below the set point of the liquid. For example, when treating a mixture containing 80 to 98% dioctyl diphenylamine, the coolant may have a temperature of 40-50 C. while the set point of the dioctyl diphenylamine mixture is at least about 80 C. and the initial crystallization point is about 76-79" C. With reduction in monooctyl diphenylamine in the mixture to from 2 to 10% by weight, the set point of the mixture will be at least about 85 C. The temperature of the mixture being cooled, however, may be about 85 to 100 C. for after crystallization has been initiated the temperature of the mixture may rise somewhat and remain constant although it can be maintained at about its initial crystallization point if desired. The agitating means keeps the temperature of the mixture constant while continuously withdrawing heat until about 55 to 80% of the latent; heat of crystallization has been withdrawn. Unless this; heat is removed rapidly and continuously from the mix-- ture, it would fail to crystallize since as fast as the heat. of crystallization is given off to produce a solid it would be readsorbed by the system to cause melting. After 55% of this heat has been removed, the semi-solid material is cooled at a lower temperature where the remaining heat of crystallization is removed. This may be accomplished by placing the semisolid in heat exchange relationship with a material having a temperature of about 1020 C. At this point the material will have cooled sufiiciently so that with the rapid reduction in temperature it solidifies without further agitation being required. It would not be desirable to completely cool in the first step to the solid phase since, although this method can be done, it will cause solidification within the apparatus used requiring a shutdown in operations until the solid can be removed and the agitating means freed. A sufiicient amount of heat is, accordingly, withdrawn in the first step so that when the semisolid is rapidly cooled in the second step, it will solidify into a hard, frangible, dry material.

The solid, frangible, dry antioxidant produced by the method of the present invention will contain a predominating amount and preferably from to 98% by weight of the dialkylated diarylamine having the formula:

R Ra Ra RA 1 l H l I where R1, R2, R3 and R4 are selected from the group consisting of halogen, hydrogen and alkyl having from 1 to 4 carbon atoms and R5 and R6 are alkyl having from 6 to 12 carbon atoms and a minor amount, preferably from 2 to 20% by weight, of a monoalkylated diarylamine having the formula:

R1 R2 R1 R4 7 l l 111 I where R1, R2, R3 and R4 are selected from the group consisting of halogen, hydrogen and alkyl having from 1 to 4 carbon atoms and R5 is alkyl having from 6 to 12 carbon atoms. Still more preferred compositions are those in which the dialkylated diarylamine is present in an amount of from to 98%, the balance being the monoalkylated diarylamine. The set point of the solid mixture will be within from about 3 to 20% of the set point of the pure dialkylated diarylamine contained in the mixture.

The following examples will serve to illustrate the invention with more particularity to those skilled in the art:

EXAMPLE I One mol of diphenylamine was charged to an autoclave and heated to C. using moderate speed agitation with an anchor-type agitator. When the temperature reached 140 C., about 0.0125 mol of aluminum chloride was added. The temperature rose rapidly to C. Then 3 mols of diisobutylene were charged taking a period of about 20 minutes for the addition. The temperature was allowed to rise to approximately C. and the pressure increased to 30-60 p. s. i. g. When the addition of the diisobutylene was complete, agitation was continued an additional 45 minutes. After the charge was cooled to 90 C., it was washed with water and 50% caustic soda solution and distilled. Unreacted diisobutylene was recovered but no unreacted diphenylamine was recoverd. The remainder of the charge was distilled under vacuum (1-10 mm. Hg absolute) at a pot temperature of 250 C. to recover a major proportion of the monooctyl diphenylamine as the distillate. The residue contained about 5% by weight of monooctyl diphenylamine, the balance being the p,p'-dioctyl diphenylamine. The liquid residue was then permitted to cool to about 100 C. and pumped into a tube fitted with an agitator which was rapidly rotated while the tube was cooled with water at a temperature of about 65 C. The residue passed through the tube in about 6 seconds (200 lbs./hr.) wherein about 70% of its latent 5 And ei crystulli'zation wes romovod flflfi WfiSfifilflldCd asaa at a temperature of 90 onto a stain- -icwstpdlwonveyor=jbettcoolcd toabout 10*:(3; Imabout lammonds the 'semisolidmass lind 'beceme --a=-frangib1e, hadlllrymolid whichcould be -eesily-breken up in a itliad aset point of about 86 "C.

.IEXAMPLEIJI -The-rpmduct:of ExampleItatbosre was readily-handled rmilhzsthedconveptionals rubber- -compounding ingredients :mrxmmbber miilitoa formr-a composition which ynszcumdranditested. rAacoltrol without-any antioxidant 4mtalsosprcpanedioncomparativetdata. ffhetcomponents :nfithe; rubberyacompositionsand :the insults obtained on arcsshown belowr Compositionsofirubbers i- M. m. a- L Parts by Parts by Components ,Weighcv Weight I with Solid "without stvtioxldant Annulme Pale crepe 100 100 Stearic acid 2 2 Zinc oxide 5 TlOs a- 50 50 Sulfur 2. 75 2, 75 Benzothiazyl Disulfide 1 1 Tetramethyl Thiuram Disulfide .l 0. 1 0. 1 Antioxidant 1 Tensile properties of rubber compositions [Modulus 300% (M)tensile (T)-percent elongation (E)hardness (H) Press Cures at 290 F.

M '1 E H M 'I E H Uncured.

AFTER 4 DAYS IN OXYGEN BOMB AT 80 C.

Press Cures at 290 F.

M T E H M T E H 5 min min 820 3,020 520 46 580 l, 480 470 40 16 min 980 2,680 470 49 560 680 360 40 20min 960 2,340 450 48 30 min 800 2, 260 480 45 0) 1 Melted in O. B.

AFTER 7 DAYS IN OXYGEN BOMB AT 80 C.

(A) Press Cures at M 'I E H M '1 E H and Min. Cures (A) (B) Dulux Low Bake Panel Dulux Baked 307300 Hoe The above examples show that a dialkylated diarylamine composition can readily be solidified and then employcdsin compotmding rubber to which it 'Will'ja'iiord --antli'oxidant properties as well as non staining properties.

agitationthe-resulting liquidresidue mixture to aboutits set point until a semisolid "is obtainedqandthen rapidly coolingwell below-its set point. The solid product is easily crushed-and-can bereadily handled-on rubber mills --by compounders.

, *Having "thus described theinvention what is claimed as new andnovel and is desired to'besecurcd by U. S.

Letters Patent --is 1. The method which comprises agitating a liquid composition comprising essentially from Y to y 98% by weight of=-p,p-'-di1;l,3;3 tetramethyl butyl diphenylamine and the balancep-lglg3 ;3-tetramethyl -butyl diphenylamineawhilecoolingnto a' temperature 1 of from about to 100 C. to provide a semisolid mass and then rapidly cooling said mass to a temperature substantially below the initial crystallization point temperature of the composition to provide a solid, frangible, dry composition having a set point of at least about 80 C.

2. The method which comprises agitating a liquid composition comprising essentially from to 98% by weight of p,p-di-1,1,3,3-tetramethyl butyl diphenylamine and the balance p-1,l,3,3-tetramethyl butyl diphenylamine while cooling to a temperature of from about 85 to 100 C. to provide a semisolid mass and then rapidly cooling said mass to a temperature substantially below the initial crystallization point temperature of the composition to provide a solid, frangible, dry composition having a set point of at least about 85 C.

3. The method which comprises agitating a liquid composition comprising essentially about by weight of p,p'-di-1,1,3,3-tetramethyl butyl diphenylamine and the balance p-1,l,3,3-tetramethyl butyl diphenylamine while cooling to a temperature of from about 85 to C. to remove about 70% of the latent heat of crystallization and provide a semisolid mass and then immediately bringing said mass without agitation into heat exchange relationship with cooling means at a temperature of from about 10 to 20 C. to remove the balance of the latent heat of crystallization to provide a solid, frangible, dry composition having a set point of about 86 C.

4. The method which comprises agitating in a first zone a liquid composition consisting essentially of a major amount of p,p'-di-1,1,3,3-tetramethyl butyl diphenylamine and a minor amount of p-1,1,3,3-tetramcthyl butyl diphenylamine while cooling said liquid composition to a temperature within the range of the initial crystallization point temperature of said liquid composition to the set point temperature of said dialkylated diphenylamine to obtain a semisolid composition, delivering said semisolid composition to a second zone, and then without agitation in said second zone rapidly cooling said semisolid compo sition below the initial crystallization point temperature of the liquid composition to provide a solid, frangible, dry composition.

5. The method which comprises delivering to a first zone a liquid mixture consisting essentially of from 80 to 98% by weight of p,p'-di-l,1,3,3-tetramethyl butyl diphenylamine and from 20 to 2% by weight of p-1,1,3,3 tetramethyl butyl diphenylamine, rapidly passing said liquid mixture through said first zone, agitating said liquid mixture and cooling the same while passing said mixture through said first zone to withdraw from about 55 to 80% of the latent heat of crystallization from said liquid mixture and thereby to form a semisolid mixture, delivering said semisolid mixture to a second zone, and rapidly cooling said semisolid mixture in said second zone substantially below the initial crystallization point temperature of said liquid mixture to remove the balance of the latent heat of crystallization and to provide a solid,

frangible, dry mixture having a set point of at least about 6. The method which comprises continuously delivera ing to a first zone a liquid composition consisting essentially of from 90 to 98% by weight of p,p'-di-1 ,1,3,3 tetramethyl butyl diphenylamine and from to 2% by [weight of p-1,1',3,3-tetramethyl butyl diphenylamine,

' through said first zone until from about to 80% of the latent heat of crystallization of said mixture has been withi drawn to form a semisolid mass, delivering said semisolid mass to a second zone and rapidlycooling said mass in said second zone substantially below the initial crystallization point of said liquid composition without agitation ,to provide a solid, frangible, dry mixture having a set point within from about 3 to 20% of the set point of the pure p,p'-di-l,1,3,3-tetramethyl butyl diphenylamine.

7. The method which comprises continuously pumping a-liquid composition having a temperature ofv about 100 C. and'eomprising essentially about 5% by weight of p- 1,1,3,3-tetramethyl butyl diphenylamine and the balance p,p-di-1,1,3,3-tetramethyl butyl diphenylamine througbja first zonewhich contains a rapidly rotating agitator in contact with said composition and which is in heat ex change relationship with a coolant at about C. and at a rate of about 200 lbs./hr. to remove about of the latent heat of crystallization of said liquid composition, extruding said composition as a semisolid mass having a temperature of C. from said first zone onto conveying means having a temperature of about 10 C. to remove the balance of the latent heat of crystallization from said composition and to provide a frangible, hard, dry solid having a set point of about 86 C.

References Cited in the file of this patent UNITED STATES PATENTS Craig July 30, 1935 2,530,769 Hollis Nov. 21, 1950 

1. THE METHOD WHICH COMPRISES AGITATING A LIQUID COMPOSITION COMPRISING ESSENTIALLY FROM 80 TO 98% BY WEIGHT OF P,P''-DI-1,1,3,3-TETRAMETHYL BUTYL DIPENYLAMINE AND THE BALANCE P-1,1,3,3-TETRAMETHYL BUTYL DIPHENYLAMINE WHILE COOLING TO A TEMPERATURE OF FROM ABOUT 85 TO 100*C. TO PROVIDE A SEMISOLID MASS AND THEN RAPIDLY COOLING SAID MASS TO A TEMPERATURE SUBSTANTIALLY BELOW THE INITIAL CRYSTALLIZATION POINT TEMPERATURE OF THE COMPOSITION TO PROVIDE A SOLID, FRANGIBLE, DRY COMPOSITION HAVING A SET POINT OF AT LEAST ABOUT 80*C. 